advent-of-code/2023/day8.rb

44 lines
787 B
Ruby
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2023-12-08 11:25:22 +00:00
START = "AAA"
FINISH = "ZZZ"
class Node
attr_reader :name, :left, :right
def initialize(name, left, right)
@name = name
@left = left
@right = right
end
end
raw_instructions, raw_nodes = ARGF.read.split("\n\n")
nodes = Hash.new
raw_nodes.each_line do |line|
next if line.empty?
if line =~ /^([A-Z]+) = \(([A-Z]+), ([A-Z]+)\)$/
nodes[$1] = Node.new($1, $2, $3)
else
throw "unmatched line #{line}"
end
end
node = nodes[START]
instructions = raw_instructions.split("").cycle
steps = 0
while node.name != FINISH
steps += 1
instruction = instructions.next
case instruction
when "L"
node = nodes[node.left]
when "R"
node = nodes[node.right]
else
throw "unexpected instruction: '#{instruction}'"
end
end
puts "Part 1: #{steps}"